I want to save library feature parts in a Dropbox folder so that I can access them from different workstations at different work locations.
If I do this, the feature doesn't appear in the selection list, e.g. weldment profiles.
Instead, the only way I can make the parts appear in the dropdown selection list is to save them the Solidworks default library feature folder on the C: drive.
Did you added the path for the Dropbox location on under Tools > Options > File location.
I just tested it again for both weldment profiles and forming tools in design library and both are working without a glitch.